1. "Wireless applications in industry: the aluminum industry as a prototype" Prof. James W. Evans Dept. of Materials Science and Engineering, UCB Collaborators: Mike Schneider, Prof. Paul Wright (Dan Steingart, Andrew Redfern & Nathan Ota) Support from UCEI & Honeywell

2. Outline 1. Introduction – energy consumption by industry, the production of aluminum. 2. Why wireless instrumentation? 3. Overview of wireless sensing devices 4. Previous campaigns 5. Campaign in April, 2005 at Eastalco 6. Conclusion from work so far 7. Other industries?

3. From Energy Information Administration 2002 statistics US production of energy (all uses): 70.8 quads US production of energy (all uses): 70.8 quads US consumption of energy for manufacturing: US consumption of energy for manufacturing: 22.7 quads of which electricity is 832 trillion kWh Electrical energy consumption by primary aluminum industry in US: 56.7 trillion kWh Electrical energy consumption by primary aluminum industry in US: 56.7 trillion kWh

4. Aluminum – the good news Use of aluminum in vehicles, rather than steel, reduces vehicle weight significantly = improved gas mileage = lower CO 2 emissions. Use of aluminum in vehicles, rather than steel, reduces vehicle weight significantly = improved gas mileage = lower CO 2 emissions. Aluminum beverage can recycling is an environmental success story. Aluminum beverage can recycling is an environmental success story. Use of aluminum in construction, rather than wood, conserves forests. Use of aluminum in construction, rather than wood, conserves forests.

5. Aluminum – the bad news Primary production of aluminum consumes large amounts of electrical energy – more than the electricity consumed by the whole of France. Primary production of aluminum consumes large amounts of electrical energy – more than the electricity consumed by the whole of France. Primary production of aluminum generates large amounts of greenhouse gasses. E.g. in 1997 110 million tonnes of CO 2 equivalents, of which 50 million tons of CO 2 equivalents were PFCs. Primary production of aluminum generates large amounts of greenhouse gasses. E.g. in 1997 110 million tonnes of CO 2 equivalents, of which 50 million tons of CO 2 equivalents were PFCs.

6. Aluminum industry Major primary producers: Major primary producers:USCanadaRussiaChinaNorway 23 smelters in US a few years ago, now 19

9. Energy consumption per kg of Al over last century

12. Hall (- Héroult) cells About size of a shipping container. About size of a shipping container. Contain molten fluoride electrolyte at 950- 960 0 C. Contain molten fluoride electrolyte at 950- 960 0 C. Current (100-500kA) passes in through carbon “anodes”, flows through molten salt to top surface of aluminum pool then into “cathode” at bottom of cell, hence to next cell. Current (100-500kA) passes in through carbon “anodes”, flows through molten salt to top surface of aluminum pool then into “cathode” at bottom of cell, hence to next cell. Only instrumentation is voltage measurement. Only instrumentation is voltage measurement.

13. One source of fluoride emissions Contact between air and molten fluoride produces fluoride emissions. Contact between air and molten fluoride produces fluoride emissions. Contact minimized by: Contact minimized by: Maintaining frozen “crust” on top of salt Maintaining frozen “crust” on top of salt Keeping panels in place to minimize air inflow into duct system and fugitive emissions from cell. Keeping panels in place to minimize air inflow into duct system and fugitive emissions from cell. These made difficult by need to replace/adjust anodes These made difficult by need to replace/adjust anodes

14. Lack of Instrumentation Only continuous measurement is of cell voltage and current Only continuous measurement is of cell voltage and current Intermittent measurements of mass of siphoned Al, and bath temperature Intermittent measurements of mass of siphoned Al, and bath temperature What causes this lack of instrumentation? Safety concerns with wires running around potlines Safety concerns with wires running around potlines Cost of running wires Cost of running wires Possible interference with existing hardware Possible interference with existing hardware Lack of a reliable, maintenance free, continuous power sources for sensors Lack of a reliable, maintenance free, continuous power sources for sensors Solution: Energy-Scavenging Wireless Sensors

15. Wireless Sensing Technology Mote Processor-Radios (MPRs): Mica2 from Crossbow Technology, Inc., model # MPR400: Mote Processor-Radios (MPRs): Mica2 from Crossbow Technology, Inc., model # MPR400: 3rd Generation, tiny, wireless smart sensors 3rd Generation, tiny, wireless smart sensors 8 channel 10 bit ADC converter 8 channel 10 bit ADC converter FM tunable radio (set manually to 916 MHz) FM tunable radio (set manually to 916 MHz) Transmit up to 500 feet outdoors with a 1/2 wave dipole antenna Transmit up to 500 feet outdoors with a 1/2 wave dipole antenna Draws maximum 26 mA (@ 3V  ~80mW) in full power mode Draws maximum 26 mA (@ 3V  ~80mW) in full power mode (8  A in sleep mode) (8  A in sleep mode)

16. Objectives of Eastalco campaigns 1. Test concept of wireless cell monitoring (would strong magnetic fields interfere with wireless devices?). 2. Monitor conditions in duct from a cell (pressure or temperature) to see if cell crust intact and cover panels in place (so as to minimize emissions). 3. Measure heat flux from shell of a cell (perhaps a diagnostic for sidewall condition). 4. Test notion of powering wireless devices by “energy scavenging”, rather than batteries.

17. Campaigns at Eastalco Early 2004: Early 2004: Duct pressure measurement successful but useless Duct pressure measurement successful but useless Motes undisturbed by magnetic field and communicate properly (about 100 ft) Motes undisturbed by magnetic field and communicate properly (about 100 ft) Late 2004: Late 2004: Motes self powered from thermoelectric generators (TEGs) Motes self powered from thermoelectric generators (TEGs) Development of DC-DC power conditioning for TEGs Development of DC-DC power conditioning for TEGs Successful duct temperature measurement Successful duct temperature measurement Magnetically attached motes Magnetically attached motes

18. Mechanical Design #1 – Duct Insert TEG Housing Thermistor Housing 7” extension into Exhaust Duct Cutaway view of Heat Sink Single Tellurex TEG Mica 2 Mote DC/DC Converter Hot Plate V2 (designed for specific TEG) 1”

19. Complete Assembly Hot side machined to the curvature of the duct Heat Sink (cold side) 7” extension into duct Thermistor Mica 2 Mote DC/DC Converter

20. Cross-Cut Heat Sink Mechanical Design #2 - Magnetically Attachable TEG Housing Use same electronics in previous design Use same electronics in previous design Can be placed on any flat ferromagnetic material w/ Temp < 225 o C Can be placed on any flat ferromagnetic material w/ Temp < 225 o C Samarium-Cobalt magnets TEG Cross-Cut Heat sink

21. Experimental results – Networking Capabilities Sample Trial Thermoelectrically powered 3 / Node 1 removed Node 3 added

22. Experimental results – Networking Base Station 15’ 20’ Thermoelectrically powered nodes ID = 7 6 9 10 1 12 3 11 13 14 = Cell Legend: = Mote *Note: All nodes were battery powered unless otherwise noted 8

23. Last two campaigns at Eastalco (March/April, 2005) Eleven motes/laptop at Eastalco for approx three weeks Eleven motes/laptop at Eastalco for approx three weeks Four motes powered from thermoelectric generators (TEGs) Four motes powered from thermoelectric generators (TEGs) Measurement of heat flux from shell & gas temperature in duct Measurement of heat flux from shell & gas temperature in duct Data transferred by internet to ATC and UCB Data transferred by internet to ATC and UCB

24. April 2005 at Eastalco; mote layout

25. Last campaign – representative results Anode change? Pot tending?

26. Duct temperature and shell heat flux, “day 5”

27. Nine days of data SunMon

28. Conclusions from past work Wireless instrumentation of pots has been demonstrated (for a period of about two weeks) Wireless instrumentation of pots has been demonstrated (for a period of about two weeks) The wireless devices (sensing motes and relay motes) can be self powered using TEGs The wireless devices (sensing motes and relay motes) can be self powered using TEGs Gas temperatures in pot ducts carry signatures of correct (or incorrect) pot operation Gas temperatures in pot ducts carry signatures of correct (or incorrect) pot operation Heat fluxes from pots are at very far from steady state – show diurnal variation probably due to variation of potroom temperature – statistical/modeling treatment needed for reliable value. Heat fluxes from pots are at very far from steady state – show diurnal variation probably due to variation of potroom temperature – statistical/modeling treatment needed for reliable value.

29. Applications of wireless technology to Hall cells – why a good prototype study Hall cells ideal test case because of: Limited instrumentation at present Limited instrumentation at present Significant energy consumption (and energy efficiency only approx. 45%) Significant energy consumption (and energy efficiency only approx. 45%) Safety issues in wired instrumentation Safety issues in wired instrumentation Large number of cells per plant (few hundred in a “potline”) and large number of plants Large number of cells per plant (few hundred in a “potline”) and large number of plants Opportunities for energy scavenging to power sensors and electronics Opportunities for energy scavenging to power sensors and electronics

30. What’s in the future? Complete instrumentation of an aluminum smelter (not just duct temperatures). Complete instrumentation of an aluminum smelter (not just duct temperatures). Instrumentation of similar plants (copper, zinc, magnesium, chlor/alkali ….) Instrumentation of similar plants (copper, zinc, magnesium, chlor/alkali ….) Application to other industries (papermaking, weaving, petrochemicals…..). Best when: Application to other industries (papermaking, weaving, petrochemicals…..). Best when: Many “small” production units Many “small” production units Instrumentation presently lacking but valuable Instrumentation presently lacking but valuable Cost/safety inhibit wired sensors Cost/safety inhibit wired sensors Opportunity for energy scavenging Opportunity for energy scavenging